Cushioning structure for hydraulic cylinders



CUSHIONING STRUCTURE FOR HYDRAULIC CYLINDERS I Sept 9, 1958 M. E.HALLADAY Original iled Jan. 11, 1954 l? 54a /4 E E m m v m K ATTORNEYRe. 24,532 Reissued Sept. 9, 1958 CUSHIONING STRUCTURE FOR HYDRAULICCYLINDERS Merton E. Halladay, Jackson, and Charles W. White,

Clarklake, Mich., assignors to Tomkins-Johnson Company, Jackson, Mich.,a corporation of Michigan Original No. 2,804,052, dated August 27, 1957,Serial No. 403,158, January 11, 1954. Application for reissue April 30,1958, Serial No. 734,378 1 1 Claim. (Cl. 121-38) Matter enclosed inheavy brackets appears in the original patent but forms no part of thisreissue specification; matter printed in italics indicates the additionsmade by reissue.

This invention relates to improvements in the means employed forcushioning and regulating the movement of reciprocated pistons actuatedby a fluid, such as oil, air, and the like in which structure isemployed, movable with the piston, to restrict the flow of the fluidmoving ahead of the piston so as to cushion and regulate the movement asthe piston reaches the end of its stroke in one direction or in theopposite direction.

It is an object of the invention to provide improved means for effectingsuch flow restricting and cushioning action in a simple yet efiicientmanner with the employment of the fewest number of parts, which can bestandardised and manufactured without the need for close manufacturingtolerances and are capable of being readily installed, or replaced.

The above and other objects and advantages of the invention, residing inthe construction, arrangement and combination of parts will appear clearfrom a consideration of the following descriptions with reference to theaccompanying drawings and from the appended claim.

In the drawings:

Fig. l is a longitudinal section on the line II of Fig. 3 of a pistonand cylinder assembly incorporating fluid flow restricting andcushioning means in accordance with the invention and shown in positionwhen the piston is moved to the left, as indicated by the arrow A,

Fig. 2 is a similar view to Fig. 1, but with the piston shown moved tothe right, as indicated by the arrow B, and

Fig. 3 is a cross section on the line IIIIH of Fig. 1.

Referring to the drawings indicates the cylinder, which has heads 12secured thereto at its opposite ends in any suitable manner, as by thescrew-threading 14.

The piston, indicated at 16, is supported for reciprocation in thecylinder and has its piston rod 18, upon which sealing plugs 20 and 22are secured so as to engage the opposite sides of the piston, with thenut 24 holding the parts in position.

To alternately direct fluid under pressure against opposite sides of thepiston 16, any suitable conduit (not shown) connects the ports 26 and 28with a source of the pressure fluid, there being a valve .provided (notshown) for alternatively connecting these parts to receive the pressurefluid for admission against one side of the a piston and foralternatively connecting them for exhaust of the pressure fluid. Thus,if the port 26 is connected to admit pressure fluid against theleft-hand side of the piston the port 28 will be connected to exhaustthe pressure fluid from the right-hand side of the piston, and viceversa.

The means provided for restricting the fluid and cushioning the pistonmovement as it reaches the end of its stroke in either directioncomprise a pair of similar slotted rings 30 and 32, with associated stoprings 34, and

restricted flow passages 36, 36 and 38, 38' provided in the left-handand the right-hand piston heads 12, respectivel Tli e slotted rings 30and 32 are mounted for axial movement within annular spaces 40 definedbetween the cylinder heads 12 and the piston rod plugs 20 and 22, theirmovement being limited by internal radial abutment surfaces 42 on eachcylinder head and by the stop rings 34. These slotted rings also havesome freedom of movement to float vertically within their confiningspaces 40 and with respect to the said radial abutment surfaces 42,whereby to provide for a self centering movement of these rings in thepiston cushioning movements and eliminate the necessity of providingprecision concentric surfaces. The stop rings 34 are shown securedwithin annular recesses on the interior surfaces of the cylinder heads12, and the piston plugs 20 and 22 are shown with bevelled end surfaces20 and 22' which assist in leading the plugs into their respectiveslotted rings and effect the initial cushioning of the piston.

The slotted rings 30 and 32 are of similar construction, as will be seenfrom reference to the drawings. Each ring is formed on its exteriorsurface with a series of circumferentially spaced arcuate slots 44,which extend the full-axial extent ofthe rings and define axial fluidflow passages, the slots being separated by radial integral web portions46 of the rings, which web portions have relative axial sliding andvertical floating movement with respect to the interior cylinder headsurfaces.

On each side of each of the slotted rings, as presented to thecorresponding stop ring, the rings are formed with internal counterbores48 and on their opposite sides, as presented to the cylinder headabutment surfaces 42, the rings are formed with external counterbores52.

The restricted fluid flow passages 36, 36' and 38, 38 communicatewith-intermediate passages 36" and 38", respectively, in which valveplugs 54 are located for adjustment by the nuts 56 so as to adjust theeffective size of the opening between the passages 36", 36' and 38",38'. Such adjustment may be an initial set adjustment made to suit aparticular cylinder and piston assembly.

In operation, with pressure fluid admitted through port 28 and port 26being connected to exhaust, and having reference to Fig. 1, the pressurefluid will act against the slotted ring 32 to move it to the leftagainst the corresponding stop ring 34. This opens up the slots 44 to aflow of the fluid from the port 28 to the right-hand side of the piston,with attendant movement of the piston to the left, insertion of thesealing plug 20 in the slotted ring 30, and seating of the slotted ring30 against the abutment surface 42 on the left-hand cylinder headsurface 42. This seating of the ring 30 gives rise to the formation of arestriction within the cylinder space C formed on the left-hand side ofthe piston, as seen in Fig. 1, due to the flow of the fluid from thiscylinder space to the exhaust port 26 being constrained to take placethrough the restricted passageway 36, 36", 36 via the slots 44 in thering 30. These slots 44, with the ring 30 floatingly seated against thesaid surface 42, will be open to a flow of the fluid from the cylinderspace C but will be closed to the exhaust port 26 except through thesaid passages 36, 36", 36.

The reverse action takes place when the piston is moved to the rightfrom the position seen in Fig. 1 .to the position seen in Fig. 2, wherethe slotted rings 30 and 32 are shown reversed in position and the fluidcushion is formed in the cylinder space D on the right of the piston 16.

Having thus described our invention, what we claim as novel and desireto protect by Letters Patent is as follows:

A piston and cylinder assembly having a fluid cushion for cushioning thepiston travel at the ends of its stroke comprising a cylinder forcylinder heads at opposite ends thereof, a centrally located boredefined in [each] at least one of said heads for the passage ofactuating and exhaust fluids in opposite directions, a cylindricalpiston disposed in said cylinder for actuation by differential fluidpressure on opposite sides'of said piston and having a piston rodconnected thereto, a cylindrical memberlzs] of lesser diameter than saidpiston and located upon [opposite sides] the bore sideof'said piston and[alternatively] movable into said bore[s] [of said heads] as the end of[each] a stroke of said piston is approached to restrict the passage ofexhaust fluid through said bore[s], a ring valve[s] supported in saidbore[s] for limited axial and radial movement, the internal diameter ofsaid ring valve[s] approaching the external diameter of said cylindricalmember[s] to provide a sliding sealbetween said'ring valve[s] and saidcylindrical memberIIs] and imparting limited movement to said ringvalve[s] in the direction of piston movement, port structure definedalong the periphery of said ring valve[s] for controlled passage offluid through said boreljs], and abutment structure located in saidbore[s] and providing a seat for-said ring valve[s] for regulating saidport structure upon axial movement of said ring valve[s], said abutmentstructure and said ring valve[s] coacting in, said bore| 's] andproviding a seat for said ring valve[s] for regulating said portstructure upon axial movement of said ring valve[s], and saidcylindrical memberIIs] and said ring valve[s] coacting in said boreEs]to restrict the exhausting of fluid from said cylinder as the pistonapproaches from one direction the end ofits stroke to provide a fluidcushion, upon piston movement in the opposite direction said ringvalve[s] being axially moved to open said port structure for theadmission of actuating fluid to said cylinder.

References Cited in'the file of this patent or the original patentUNITED STATES PATENTS 1,956,758 Ernst May 1, 1934 2,493,602 SterrettIan. 3, 1950 2,556,698 Loewe June 12, 1951 2,704,996 Peterson Mar. 29,1955 2,710,595 Peterson June 14, 1955 2,719,510 Elder Oct. 4, 1955

